The invention relates to a method for controlling a drivetrain having an internal combustion engine, a dual-clutch transmission, having a first and second sub-transmission having at least one shiftable gear ratio, a first friction clutch disposed between the internal combustion engine and the first sub-transmission and a second friction clutch disposed between the internal combustion engine and the second sub-transmission to provide a drivetrain torque at a transmission output of the dual-clutch transmission by transferring an engine torque adjusted thereto via the friction clutches.
From DE 10 2005 036 894 A1 , FIG. 1 of which is reproduced in this case, a drivetrain 1 of this species is known, having a parallel shift transmission 16 as a dual-clutch transmission, wherein the engine torque of the internal combustion engine, delivered by the crankshaft 10, controlled by means of a dual clutch having two friction clutches 12, 14, is transferred via the two sub-transmissions 16a, 16bto a transmission output 18. When a friction clutch 12, 14 assigned here to one sub-transmission 16a, 16bis disengaged, the gear ratios are shifted and deselected. The actual shifting of the dual-clutch transmission 16 takes place with gear ratios (defined by gears 1, 2, 3, 4, 5, 6, R)selected in both sub-transmissions, 16b, 16a, by means of a so-called overlapping shift mechanism, known, for example, from WO 2007/124710 A1, wherein the engaged friction clutch 12, 14 of one sub-transmission 16a, 16bwhich is transferring torque is disengaged, and the disengaged friction clutch 14, 12 of the other sub-transmission 16b, 16ais engaged in an overlapping manner. The clutch arrangements 12, 14 here are shown in a housing 34 with spring damper arrangements 36, 38 between the clutches and the concentric transmission input shafts 40, 42. Within the sub-transmissions 16a, 16b , the different transmission ratios are indicated at 52, 54, 56, 68, 60, 62, 64, 66, and the associated transmission gears are indicated as 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94. The friction clutches are designed here with regard to their transfer capacity so that at least the maximum engine torque is transferable when the friction clutch is completely engaged. As this occurs, the engine torque and the clutch torques of the friction clutches are ascertained or estimated constantly over their service life. If it is found that, for example, due to previous damage to a friction clutch, its transfer capacity is no longer adequate for a present enginetorque, the engine torque is limited to the clutch torque which is still transferable via the friction clutch in question. This results in performance losses in the drivetrain, with the sub-transmission being operated with the limitedly functional friction clutch.